| Message ID | 1427264236-17249-2-git-send-email-hannes@cmpxchg.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, 25 Mar 2015, Johannes Weiner wrote: > Setting oom_killer_disabled to false is atomic, there is no need for > further synchronization with ongoing allocations trying to OOM-kill. > > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> > --- > mm/oom_kill.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 2b665da1b3c9..73763e489e86 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -488,9 +488,7 @@ bool oom_killer_disable(void) > */ > void oom_killer_enable(void) > { > - down_write(&oom_sem); > oom_killer_disabled = false; > - up_write(&oom_sem); > } > > #define K(x) ((x) << (PAGE_SHIFT-10)) I haven't looked through the new disable-oom-killer-for-pm patchset that was merged, but this oom_killer_disabled thing already looks improperly handled. I think any correctness or cleanups in this area would be very helpful. I think mark_tsk_oom_victim() in mem_cgroup_out_of_memory() is just luckily not racing with a call to oom_killer_enable() and triggering the WARN_ON(oom_killer_disabled) since there's no "oom_sem" held here, and it's an improper context based on the comment of mark_tsk_oom_victim(). There might be something else that is intended but not implemented correctly that I'm unaware of, but I know of no reason why setting of oom_killer_disabled would need to take a semaphore? I'm thinking it has something to do with the remainder of that comment, specifically the "never after oom has been disabled already." Michal? -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed 25-03-15 02:17:05, Johannes Weiner wrote: > Setting oom_killer_disabled to false is atomic, there is no need for > further synchronization with ongoing allocations trying to OOM-kill. True, races with an ongoing allocations are not harmful. > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.cz> > --- > mm/oom_kill.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 2b665da1b3c9..73763e489e86 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -488,9 +488,7 @@ bool oom_killer_disable(void) > */ > void oom_killer_enable(void) > { > - down_write(&oom_sem); > oom_killer_disabled = false; > - up_write(&oom_sem); > } > > #define K(x) ((x) << (PAGE_SHIFT-10)) > -- > 2.3.3 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
On Wed, 25 Mar 2015, Johannes Weiner wrote: > Setting oom_killer_disabled to false is atomic, there is no need for > further synchronization with ongoing allocations trying to OOM-kill. > > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: David Rientjes <rientjes@google.com> -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 2b665da1b3c9..73763e489e86 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -488,9 +488,7 @@ bool oom_killer_disable(void) */ void oom_killer_enable(void) { - down_write(&oom_sem); oom_killer_disabled = false; - up_write(&oom_sem); } #define K(x) ((x) << (PAGE_SHIFT-10))
Setting oom_killer_disabled to false is atomic, there is no need for further synchronization with ongoing allocations trying to OOM-kill. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> --- mm/oom_kill.c | 2 -- 1 file changed, 2 deletions(-)